Abstract

Complex 3D micro-tissues and organoids are becoming widespread in drug-screening technologies, but have been used sparingly for cell therapy as current approaches for producing self-organized cell clusters lack scalability or reproducibility in size and cellular organization. To address this challenge, we have engineered complex 3D micro-tissues consisting of a blood vessel core and a mesenchymal stem cell shell that can act as building blocks in a new vascular network for regenerative medicine. The micro-tissues are small enough to be injected, and the core-shell structure protects them from the shear stress of injection. The microtissues’ injectability enables direct delivery of vascular building blocks to diseased areas, thereby obviating surgery in ischemic tissues with impaired wound healing. We introduced a method of using hydrogels as sacrificial scaffolds and a growth factor regime, which allows cells to form self-organized clusters followed by gentle release, resulting in highly-reproducible multicellular structures on a large scale. We demonstrated this strategy for endothelial cells and mesenchymal stem cells to self-organize into blood-vessel units, which were injected into mice, and rapidly formed perfusing vasculature. Moreover, in a mouse model of peripheral artery disease, intramuscular injections of blood-vessel units resulted in rapid restoration of vascular perfusion within seven days. As cell therapy transforms into a new class of therapeutic modality, this simple method – making use of the dynamic nature of hydrogels – could offer high yields of self-organized multicellular aggregates with reproducible sizes and cellular architectures.